Technical Field
The present invention relates to a rotor blade element for a wind turbine, a rotor blade, and a production process for the rotor blade element or the rotor blade. The invention further relates to a wind turbine.
Description of the Related Art
Rotor blades for wind turbines have been known for a long time and are described by way of example in DE 10 2004 007 487 A1 and DE 103 19 246 A1. During operation they are exposed to wind pressure, erosion, temperature variations, UV irradiation and high loads due to precipitation. With blade tip velocities up to 300 km/h, sand grains, salt particles, insects or other objects carried by the air have an abrasive effect. This wears the surface of rotor blades, in particular in the frontal edge region. At these locations there is ablation of the rotor surface and therefore a loss of aerodynamic properties and stability.
However, at the same time the rotor blades are intended to have minimum weight, in order to minimize the bending loads acting on any scarring that may be present on the rotor blade, and on the attendant bearings and the tower of the wind turbine. It has proved to be advantageous to produce rotor blades from individual elements and to bond these elements to one another to give a hollow-chamber rotor blade. Rotor blade elements usually used are a rotor blade pressure side, a rotor blade suction side and one or more bonding fillets for the bonding and stiffening of the rotor blade pressure side and rotor blade suction side. Success has likewise been achieved with one-piece production of the rotor blade pressure side and rotor blade suction side and arrangement of fillets during this production process at the locations where these are required.
Rotor blades and rotor blade elements are usually produced in a molding process in which fiber materials and/or core materials, in particular balsa wood, are inserted into a rotor blade element mold and are treated with a hardening resin to form a composite material that can withstand load. Production of rotor blades or rotor blade elements frequently uses epoxy resins as resin. These have good suitability for the construction of the base of a rotor blade or rotor blade element made of fiber material and curable resin. A person skilled in the art understands the expression “curable resin” in the context of the present invention as stating a fundamental property of the resin rather than as a property that is actually still present in a material within the rotor blade or rotor blade element.
In order to protect the rotor blades or the rotor blade elements from weathering effects and in particular from erosion, attempts have been made to use a surface layer by using a gelcoat process as described in DE 10 3 44 379 A1. This has the disadvantage that in that type of process it is necessary to provide an appropriate processing time sufficient to complete reaction of the gelcoat mixture to an extent that allows it to be covered with fiber material. This leads to undesired slowing of the production process for a rotor blade or rotor blade element. With the gelcoat process it is moreover not possible to interrupt the production of a rotor blade element or rotor blade as desired in order to permit bonding between gelcoat surface layer and infusion resin. Attempts have also been made to adhesive-bond surface foils onto the rotor blade or the rotor blade element, or to secure these by other means subsequently on the rotor blade or rotor blade element, sometimes releasably. By way of example, polyurethane foils are adhesive-bonded onto rotor blades. Another possibility from the prior art according to DE 10 2009 002 501 A1 is the production of a crosslinked composite made of surface foil and infusion resin. Again, this process is in particular possible with polyurethane foils. Polyurethane has high abrasion resistance. However, it is desirable to improve the abrasion resistance of rotor blades or rotor blade elements.
The priority application involved search of the following prior art by the German Patent and Trademark Office: DE 10 2011 004 723 A1, US 2010/0032948 A1, EP 2 416 950 B1, WO 2013/045087 A1.